static DEFINE_MUTEX(devcgroup_mutex);
+enum devcg_behavior {
+ DEVCG_DEFAULT_NONE,
+ DEVCG_DEFAULT_ALLOW,
+ DEVCG_DEFAULT_DENY,
+};
+
/*
* exception list locking rules:
* hold devcgroup_mutex for update/read.
struct dev_cgroup {
struct cgroup_subsys_state css;
struct list_head exceptions;
- enum {
- DEVCG_DEFAULT_ALLOW,
- DEVCG_DEFAULT_DENY,
- } behavior;
+ enum devcg_behavior behavior;
+ /* temporary list for pending propagation operations */
+ struct list_head propagate_pending;
};
static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
__dev_exception_clean(dev_cgroup);
}
+static inline bool is_devcg_online(const struct dev_cgroup *devcg)
+{
+ return (devcg->behavior != DEVCG_DEFAULT_NONE);
+}
+
+/**
+ * devcgroup_online - initializes devcgroup's behavior and exceptions based on
+ * parent's
+ * @cgroup: cgroup getting online
+ * returns 0 in case of success, error code otherwise
+ */
+static int devcgroup_online(struct cgroup *cgroup)
+{
+ struct dev_cgroup *dev_cgroup, *parent_dev_cgroup = NULL;
+ int ret = 0;
+
+ mutex_lock(&devcgroup_mutex);
+ dev_cgroup = cgroup_to_devcgroup(cgroup);
+ if (cgroup->parent)
+ parent_dev_cgroup = cgroup_to_devcgroup(cgroup->parent);
+
+ if (parent_dev_cgroup == NULL)
+ dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW;
+ else {
+ ret = dev_exceptions_copy(&dev_cgroup->exceptions,
+ &parent_dev_cgroup->exceptions);
+ if (!ret)
+ dev_cgroup->behavior = parent_dev_cgroup->behavior;
+ }
+ mutex_unlock(&devcgroup_mutex);
+
+ return ret;
+}
+
+static void devcgroup_offline(struct cgroup *cgroup)
+{
+ struct dev_cgroup *dev_cgroup = cgroup_to_devcgroup(cgroup);
+
+ mutex_lock(&devcgroup_mutex);
+ dev_cgroup->behavior = DEVCG_DEFAULT_NONE;
+ mutex_unlock(&devcgroup_mutex);
+}
+
/*
* called from kernel/cgroup.c with cgroup_lock() held.
*/
static struct cgroup_subsys_state *devcgroup_css_alloc(struct cgroup *cgroup)
{
- struct dev_cgroup *dev_cgroup, *parent_dev_cgroup;
- struct cgroup *parent_cgroup;
- int ret;
+ struct dev_cgroup *dev_cgroup;
dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL);
if (!dev_cgroup)
return ERR_PTR(-ENOMEM);
INIT_LIST_HEAD(&dev_cgroup->exceptions);
- parent_cgroup = cgroup->parent;
-
- if (parent_cgroup == NULL)
- dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW;
- else {
- parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup);
- mutex_lock(&devcgroup_mutex);
- ret = dev_exceptions_copy(&dev_cgroup->exceptions,
- &parent_dev_cgroup->exceptions);
- dev_cgroup->behavior = parent_dev_cgroup->behavior;
- mutex_unlock(&devcgroup_mutex);
- if (ret) {
- kfree(dev_cgroup);
- return ERR_PTR(ret);
- }
- }
+ INIT_LIST_HEAD(&dev_cgroup->propagate_pending);
+ dev_cgroup->behavior = DEVCG_DEFAULT_NONE;
return &dev_cgroup->css;
}
* verify if a certain access is allowed.
* @dev_cgroup: dev cgroup to be tested against
* @refex: new exception
+ * @behavior: behavior of the exception
*/
-static int may_access(struct dev_cgroup *dev_cgroup,
- struct dev_exception_item *refex)
+static bool may_access(struct dev_cgroup *dev_cgroup,
+ struct dev_exception_item *refex,
+ enum devcg_behavior behavior)
{
struct dev_exception_item *ex;
bool match = false;
break;
}
- /*
- * In two cases we'll consider this new exception valid:
- * - the dev cgroup has its default policy to allow + exception list:
- * the new exception should *not* match any of the exceptions
- * (behavior == DEVCG_DEFAULT_ALLOW, !match)
- * - the dev cgroup has its default policy to deny + exception list:
- * the new exception *should* match the exceptions
- * (behavior == DEVCG_DEFAULT_DENY, match)
- */
- if ((dev_cgroup->behavior == DEVCG_DEFAULT_DENY) == match)
- return 1;
- return 0;
+ if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) {
+ if (behavior == DEVCG_DEFAULT_ALLOW) {
+ /* the exception will deny access to certain devices */
+ return true;
+ } else {
+ /* the exception will allow access to certain devices */
+ if (match)
+ /*
+ * a new exception allowing access shouldn't
+ * match an parent's exception
+ */
+ return false;
+ return true;
+ }
+ } else {
+ /* only behavior == DEVCG_DEFAULT_DENY allowed here */
+ if (match)
+ /* parent has an exception that matches the proposed */
+ return true;
+ else
+ return false;
+ }
+ return false;
}
/*
if (!pcg)
return 1;
parent = cgroup_to_devcgroup(pcg);
- return may_access(parent, ex);
+ return may_access(parent, ex, childcg->behavior);
}
/**
return parent->behavior == DEVCG_DEFAULT_ALLOW;
}
+/**
+ * revalidate_active_exceptions - walks through the active exception list and
+ * revalidates the exceptions based on parent's
+ * behavior and exceptions. The exceptions that
+ * are no longer valid will be removed.
+ * Called with devcgroup_mutex held.
+ * @devcg: cgroup which exceptions will be checked
+ *
+ * This is one of the three key functions for hierarchy implementation.
+ * This function is responsible for re-evaluating all the cgroup's active
+ * exceptions due to a parent's exception change.
+ * Refer to Documentation/cgroups/devices.txt for more details.
+ */
+static void revalidate_active_exceptions(struct dev_cgroup *devcg)
+{
+ struct dev_exception_item *ex;
+ struct list_head *this, *tmp;
+
+ list_for_each_safe(this, tmp, &devcg->exceptions) {
+ ex = container_of(this, struct dev_exception_item, list);
+ if (!parent_has_perm(devcg, ex))
+ dev_exception_rm(devcg, ex);
+ }
+}
+
+/**
+ * get_online_devcg - walks the cgroup tree and fills a list with the online
+ * groups
+ * @root: cgroup used as starting point
+ * @online: list that will be filled with online groups
+ *
+ * Must be called with devcgroup_mutex held. Grabs RCU lock.
+ * Because devcgroup_mutex is held, no devcg will become online or offline
+ * during the tree walk (see devcgroup_online, devcgroup_offline)
+ * A separated list is needed because propagate_behavior() and
+ * propagate_exception() need to allocate memory and can block.
+ */
+static void get_online_devcg(struct cgroup *root, struct list_head *online)
+{
+ struct cgroup *pos;
+ struct dev_cgroup *devcg;
+
+ lockdep_assert_held(&devcgroup_mutex);
+
+ rcu_read_lock();
+ cgroup_for_each_descendant_pre(pos, root) {
+ devcg = cgroup_to_devcgroup(pos);
+ if (is_devcg_online(devcg))
+ list_add_tail(&devcg->propagate_pending, online);
+ }
+ rcu_read_unlock();
+}
+
+/**
+ * propagate_exception - propagates a new exception to the children
+ * @devcg_root: device cgroup that added a new exception
+ * @ex: new exception to be propagated
+ *
+ * returns: 0 in case of success, != 0 in case of error
+ */
+static int propagate_exception(struct dev_cgroup *devcg_root,
+ struct dev_exception_item *ex)
+{
+ struct cgroup *root = devcg_root->css.cgroup;
+ struct dev_cgroup *devcg, *parent, *tmp;
+ int rc = 0;
+ LIST_HEAD(pending);
+
+ get_online_devcg(root, &pending);
+
+ list_for_each_entry_safe(devcg, tmp, &pending, propagate_pending) {
+ parent = cgroup_to_devcgroup(devcg->css.cgroup->parent);
+
+ /*
+ * in case both root's behavior and devcg is allow, a new
+ * restriction means adding to the exception list
+ */
+ if (devcg_root->behavior == DEVCG_DEFAULT_ALLOW &&
+ devcg->behavior == DEVCG_DEFAULT_ALLOW) {
+ rc = dev_exception_add(devcg, ex);
+ if (rc)
+ break;
+ } else {
+ /*
+ * in the other possible cases:
+ * root's behavior: allow, devcg's: deny
+ * root's behavior: deny, devcg's: deny
+ * the exception will be removed
+ */
+ dev_exception_rm(devcg, ex);
+ }
+ revalidate_active_exceptions(devcg);
+
+ list_del_init(&devcg->propagate_pending);
+ }
+ return rc;
+}
+
+static inline bool has_children(struct dev_cgroup *devcgroup)
+{
+ struct cgroup *cgrp = devcgroup->css.cgroup;
+
+ return !list_empty(&cgrp->children);
+}
+
/*
* Modify the exception list using allow/deny rules.
* CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD
{
const char *b;
char temp[12]; /* 11 + 1 characters needed for a u32 */
- int count, rc;
+ int count, rc = 0;
struct dev_exception_item ex;
struct cgroup *p = devcgroup->css.cgroup;
struct dev_cgroup *parent = NULL;
case 'a':
switch (filetype) {
case DEVCG_ALLOW:
+ if (has_children(devcgroup))
+ return -EINVAL;
+
if (!may_allow_all(parent))
return -EPERM;
dev_exception_clean(devcgroup);
return rc;
break;
case DEVCG_DENY:
+ if (has_children(devcgroup))
+ return -EINVAL;
+
dev_exception_clean(devcgroup);
devcgroup->behavior = DEVCG_DEFAULT_DENY;
break;
dev_exception_rm(devcgroup, &ex);
return 0;
}
- return dev_exception_add(devcgroup, &ex);
+ rc = dev_exception_add(devcgroup, &ex);
+ break;
case DEVCG_DENY:
/*
* If the default policy is to deny by default, try to remove
* an matching exception instead. And be silent about it: we
* don't want to break compatibility
*/
- if (devcgroup->behavior == DEVCG_DEFAULT_DENY) {
+ if (devcgroup->behavior == DEVCG_DEFAULT_DENY)
dev_exception_rm(devcgroup, &ex);
- return 0;
- }
- return dev_exception_add(devcgroup, &ex);
+ else
+ rc = dev_exception_add(devcgroup, &ex);
+
+ if (rc)
+ break;
+ /* we only propagate new restrictions */
+ rc = propagate_exception(devcgroup, &ex);
+ break;
default:
- return -EINVAL;
+ rc = -EINVAL;
}
- return 0;
+ return rc;
}
static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft,
.can_attach = devcgroup_can_attach,
.css_alloc = devcgroup_css_alloc,
.css_free = devcgroup_css_free,
+ .css_online = devcgroup_online,
+ .css_offline = devcgroup_offline,
.subsys_id = devices_subsys_id,
.base_cftypes = dev_cgroup_files,
-
- /*
- * While devices cgroup has the rudimentary hierarchy support which
- * checks the parent's restriction, it doesn't properly propagates
- * config changes in ancestors to their descendents. A child
- * should only be allowed to add more restrictions to the parent's
- * configuration. Fix it and remove the following.
- */
- .broken_hierarchy = true,
};
/**
rcu_read_lock();
dev_cgroup = task_devcgroup(current);
- rc = may_access(dev_cgroup, &ex);
+ rc = may_access(dev_cgroup, &ex, dev_cgroup->behavior);
rcu_read_unlock();
if (!rc)
projects / firefly-linux-kernel-4.4.55.git / blobdiff